<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.min.js"></script>
    <script>
        $(function() {
            var flag = false;
            $("#btn").on('click', function() {
                if (!flag) {
                    $("#d01").slideDown(3000);
                    flag = true;
                } else {
                    $("#d01").slideUp(3000);
                    flag = false;
                }
            })
        });
    </script>
    <style>
        #d01 {
            width: 200px;
            height: 200px;
            background-color: aqua;
        }
    </style>
</head>

<body>
    <div id="d01"></div>
    <button id="btn">滑动效果</button>
</body>

</html>